1. Field
The disclosure relates to devices for the manufacture of treads for tire casings.
2. Description of Related Art
To manufacture a cylindrical component that forms part of a green form of a tire, such as a tread for a tire casing for example, it is known practice to wind a strip of raw rubber onto a rotary cylindrical drum. Winding is performed over several tens of turns and at high speed. During the winding, the strip distribution means is moved in the axial direction of the drum relative to the said drum in order to form a build up of strip at the desired points and give the tread its overall shape.
It is necessary then to reduce the diameter of the drum in order to extract the said component, i.e. the tread, from it. Furthermore, it is preferable to be able to vary the diameter of the drum over a relatively large range in order to allow treads corresponding to different models of tire to be built on the same drum.
That being so, the external face of the drum on which face the rubber elements are laid needs as far as possible to have a cross section that is perfectly circular. In addition, because the rubber is raw and therefore fragile, this face must not have any reliefs or cavities liable to damage it.
Now, these various constraints are difficult to reconcile. Variable-diameter drums made up of elements of a cylinder of a given diameter which seek to achieve this are known but are unsatisfactory in so far as when the drum is brought to a diameter greater than or less than the diameter of the elements of which it is composed, the cross section of the drum is no longer a perfectly circular cross section.